This invention relates to a pre-energizer for a double acting baulkring-type synchronizer.
Baulkring-type synchronizers for use in multi-ratio transmissions are well known. Such synchronizers often include pairs of friction and jaw members for respectively synchronizing and positive clutching axially spaced apart gears to a shaft, a hub rotatably fixed to the shaft and having external spline teeth slidably receiving internal spline teeth of a shift sleeve, baulkrings having blocker teeth for arresting engaging movement of the shift sleeve until synchronization is reached and for transferring a shift force from the sleeve to friction members. Such synchronizers also often include pre-energizers having a member that is moved axially against spring force for effecting initial engagement the friction members in response to initial engaging movement of the shift sleeve.
However, when the shift sleeve is moved from a positive clutching engagement with one gear to a neutral position, the pre-energizer member may cause the friction members of the other gear to momentarily engage, thereby causing unnecessary and rapid ware of these friction surfaces. Shift sleeve movement from positive engagement with one gear to the neutral position may occur when both gears are forward drive gears but often occurs when one gear is a forward drive gear and the other is reverse drive gear. Since the relative rotational speeds of such forward/reverse gear arrangements is much greater than relative rotation of forward/forward gear arrangements, momentary engagement of the forward/reverse gears friction surfaces when shifting to neutral further increases rapid wear of these friction surfaces.
An object of this invention is to provide a baulkring-type synchronizer with an improved pre-energizer.
According to this invention, a double acting baulkring-type synchronizer selectively synchronizes and positive connects a shaft with either of axially spaced apart first and second drives that are disposed for relative rotation about an axis of the shaft and are axially fixed relative thereto. The synchronizer, as disclosed in GB-A-2 029 519 and which represents the pre-characterized of claim 1, includes a hub affixed to the shaft concentric to the axis and between the drives. The hub includes a radially extending web having axially oppositely facing sidewalls, an outer circumference having external splines, and a radially extending slot in the web extending through the outer circumference. First and second jaw teeth and first and second friction surfaces are respectively affixed to the first and second drives. A shift sleeve has internal splines slidably mating with the hub external splines and third and fourth jaw teeth respectively engagable with the first and second jaw teeth in response respectively to first and second shift forces applying axially engaging movement of the shift sleeve from a neutral position. First and second baulkrings are disposed on opposite sides of the web and respectively include third and fourth friction surfaces respectively engagable with the first and second friction surfaces to produce a synchronizing torque, and the first and second baulkrings respectively have first and second blocker surfaces. Third and fourth blocker surfaces are affixed axially relative to the shift sleeve. Pre-energizer means is for engaging the first and second friction surfaces respectively with the third and fourth friction surfaces in response to initial engaging movement of the shift sleeve by the shift forces for positioning the first and second blocker surfaces for engagement respectively with the third and fourth blocker surfaces to prevent asynchronous engagement of the first and second jaw teeth respectively with the third and fourth jaw teeth. The pre-energizer means includes a movable member axially disposed between first and second baulkring abutments and biased radially outward by spring means into a detent in the shift sleeve when the shift sleeve is in the neutral position. The detent is axially disposed between axially extending surfaces of the shift sleeve. A spring holder is disposed in the slot between the member and spring means, and has tabs slidably disposed on opposite sides of the web and ramp surfaces for centering the member thereon with a centering force determined by the angle of ramp surfaces and the force of the spring means. The detent has angled sidewalls for moving the member axially into contact with the first and second abutments in response respectively to the initial engaging movement of the shift sleeve with a force transmitting capacity greater than the centering capacity of the ramp surfaces and to move the member radially inward and onto either one of the axially extending surfaces to allow continued engaging movement of the shift sleeve for engaging the first and second jaw teeth respectively with the third and fourth jaw teeth in response to synchronization between on of the drives and the shaft.
The synchronizer is characterized by the spring holder including a platform disposed in and extending axially through the slot, the tabs embracing the web side walls in snug sliding relation, the member having axial spacing from the first and second baulkring abutments during the neutral position of shift sleeve, and the centering force provided by ramp surfaces and the axial spacing great enough to prevent movement of the member into engagement with the second abutment due to frictional forces between the member and the axially extending surfaces when the shift sleeve is moved toward the neutral position from an engaged jaw teeth jaw teeth position.